The free plasma amyloid Aß1-42/Aß1-40 ratio predicts conversion to dementia for subjects with mild cognitive impairment with performance equivalent to that of the total plasma Aß1-42/Aß1-40 ratio. The BALTAZAR study.

BACKGROUND AND PURPOSE: Blood-based biomarkers are a non-invasive solution to predict the risk of conversion of mild cognitive impairment (MCI) to dementia. The utility of free plasma amyloid peptides (not bound to plasma proteins and/or cells) as an early indicator of conversion to dementia is still debated, as the results of studies have been contradictory. In this context, we investigated whether plasma levels of the free amyloid peptides Aß1-42 and Aß1-40 and the free plasma Aß1-42/Aß1-40 ratio are associated with the conversion of MCI to dementia, in particular AD, over three years of follow-up in a subgroup of the BALTAZAR cohort. We also compared their predictive value to that of total plasma Aß1-42 and Aß1-40 levels and the total plasma Aß1-42/Aß1-40 ratio. METHODS: The plasma Aß1-42 and Aß1-40 peptide assay was performed using the INNO-BIA kit (Fujirebio Europe). Free amyloid levels (defined by the amyloid fraction directly accessible to antibodies of the assay) were obtained with the undiluted plasma, whereas total amyloid levels were obtained after the dilution of plasma (1/3) with a denaturing buffer. Free and total Aß1-42 and Aß1-40 levels were measured at inclusion for a subgroup of participants (N = 106) with mild cognitive impairment (MCI) from the BALTAZAR study (a large-scale longitudinal multicenter cohort with a three-year follow-up). Associations between conversion and the free/total plasma Aß1-42 and Aß1-40 levels and Aß1-42/Aß1-40 ratio were analyzed using logistic and Cox Proportional Hazards models. Demographic, clinical, cognitive (MMSE, ADL and IADL), APOE, and MRI characteristics (relative hippocampal volume) were compared using non-parametric (Mann-Whitney) or parametric (Student) tests for quantitative variables and Chi-square or Fisher exact tests for qualitative variables. RESULTS: The risk of conversion to dementia was lower for patients in the highest quartile of free plasma Aß1-42/Aß1-40 (≥ 25.8%) than those in the three lower quartiles: hazard ratio = 0.36 (95% confidence interval [0.15-0.87]), after adjustment for age, sex, education, and APOE ε4 (p-value = 0.022). This was comparable to the risk of conversion in the highest quartile of total plasma Aß1-42/Aß1-40: hazard ratio = 0.37 (95% confidence interval [0.16-0.89], p-value = 0.027). However, while patients in the highest quartile of total plasma Aß1-42/Aß1-40 showed higher MMSE scores and a higher hippocampal volume than patients in the three lowest quartiles of total plasma Aß1-42/Aß1-40, as well as normal CSF biomarker levels, the patients in the highest quartile of free plasma Aß1-42/Aß1-40 did not show any significant differences in MMSE scores, hippocampal volume, or CSF biomarker levels relative to the three lowest quartiles of free plasma Aß1-42/Aß1-40. CONCLUSION: The free plasma Aß1-42/Aß1-40 ratio is associated with a risk of conversion from MCI to dementia within three years, with performance comparable to that of the total plasma Aß1-42/Aß1-40 ratio. Threshold levels of the free and total plasma Aß1-42/Aß1-40 ratio could be determined, with a 60% lower risk of conversion for patients above the threshold than those below.

Indication for molecular testing by multiplex ligation-dependent probe amplification in parkinsonism.

BACKGROUND AND PURPOSE: The monogenic forms of Parkinson's disease represent <10% of familial cases and a still lower frequency of sporadic cases. However, guidelines to orient genetic testing are lacking. The aim was to establish the interest of multiplex ligation-dependent probe amplification (MLPA) as a primary screening test and to propose clinical criteria to guide genetic diagnostic tests for patients with suspected Mendelian Parkinson's disease. METHODS: In all, 567 patients with parkinsonism from 547 unrelated families were recruited and two MLPAs were performed for each. All pathogenic G2019S variants in the LRRK2 gene were confirmed by Sanger sequencing and the PRKN gene was screened for a second mutation in the cases of one heterozygous structural variant in the PRKN gene. RESULTS: The performance of MLPA was 51/567 (9%) for the entire cohort and included 27 (4.8%) LRRK2 G2019S mutations, 19 (3.4%) PRKN mutations and five (0.9%) SNCA locus duplications. The variables significantly associated with a positive test in the total cohort were North African ancestry (p < 0.0001), female sex (p = 0.004) and younger age at onset (p < 0.0008). CONCLUSIONS: Retrospective analysis allowed us to refine our indication criteria: (i) North African ancestry, (ii) an age at onset <40 years or (iii) a familial history of parkinsonism with at least one affected first-degree relative. Our study highlights the interest of MLPA testing for other parkinsonism cases with a family history, especially for patients with dementia with Lewy bodies or a multiple-system-atrophy-like phenotype.

Diagnosis associated with Tau higher than 1200 pg/mL: Insights from the clinical and laboratory practice.

CONTEXT: Cerebrospinal fluid (CSF) biomarkers are valuable tools for the diagnosis of neurological diseases. We aimed to investigate within a retrospective multicentric study the final diagnosis associated with very high CSF Tau levels and to identify patterns of biomarkers that would differentiate them in clinical practice, to help clinical biologists into physicians' counseling. PATIENTS AND METHODS: Within the national multicentric network ePLM, we included 1743 patients from January 1, 2008, to December 31, 2013, with CSF biomarkers assayed by the same Innotest assays (protein Tau, phospho-Tau [pTau], and Aß 1-42). We identified 205 patients with protein Tau concentration higher than 1200 pg/mL and final diagnosis. RESULTS: Among those patients, 105 (51.2%) were suffering from Alzheimer's disease, 37 (18%) from sporadic Creuztfeldt-Jakob disease, and 63 (30.7%) from other neurological diseases including paraneoplastic/ central nervous system tumor, frontotemporal dementia, other diagnoses, amyloid angiopathy, Lewy body dementia, and infections of the central nervous system. Phospho-Tau, Aß1-42 and Aß1-42/pTau values differed significantly between the three groups of patients (p < .001). An Aß1-42/pTau ratio between 4.7 and 9.7 was suggestive of other neurological diseases (threshold in AD: 8.3). CSF 14-3-3 was useful to discriminate Alzheimer's disease from Creuztfeldt-Jakob disease in case of Aß1-42 concentrations <550 pg/mL or pTau>60 pg/mL. CONCLUSION: This work emphasizes the interest of a well-thought-out interpretation of CSF biomarkers in neurological diseases, particularly in the case of high Tau protein concentrations in the CSF.

Mis-splicing of Tau exon 10 in myotonic dystrophy type 1 is reproduced by overexpression of CELF2 but not by MBNL1 silencing.

Tau is the proteinaceous component of intraneuronal aggregates common to neurodegenerative diseases called Tauopathies, including myotonic dystrophy type 1. In myotonic dystrophy type 1, the presence of microtubule-associated protein Tau aggregates is associated with a mis-splicing of Tau. A toxic gain-of-function at the ribonucleic acid level is a major etiological factor responsible for the mis-splicing of several transcripts in myotonic dystrophy type 1. These are probably the consequence of a loss of muscleblind-like 1 (MBNL1) function or gain of CUGBP1 and ETR3-like factor 1 (CELF1) splicing function. Whether these two dysfunctions occur together or separately and whether all mis-splicing events in myotonic dystrophy type 1 brain result from one or both of these dysfunctions remains unknown. Here, we analyzed the splicing of Tau exons 2 and 10 in the brain of myotonic dystrophy type 1 patients. Two myotonic dystrophy type 1 patients showed a mis-splicing of exon 10 whereas exon 2-inclusion was reduced in all myotonic dystrophy type 1 patients. In order to determine the potential factors responsible for exon 10 mis-splicing, we studied the effect of the splicing factors muscleblind-like 1 (MBNL1), CUGBP1 and ETR3-like factor 1 (CELF1), CUGBP1 and ETR3-like factor 2 (CELF2), and CUGBP1 and ETR3-like factor 4 (CELF4) or a dominant-negative CUGBP1 and ETR-3 like factor (CELF) factor on Tau exon 10 splicing by ectopic expression or siRNA. Interestingly, the inclusion of Tau exon 10 is reduced by CUGBP1 and ETR3-like factor 2 (CELF2) whereas it is insensitive to the loss-of-function of muscleblind-like 1 (MBNL1), CUGBP1 and ETR3-like factor 1 (CELF1) gain-of-function, or a dominant-negative of CUGBP1 and ETR-3 like factor (CELF) factor. Moreover, we observed an increased expression of CUGBP1 and ETR3-like factor 2 (CELF2) only in the brain of myotonic dystrophy type 1 patients with a mis-splicing of exon 10. Taken together, our results indicate the occurrence of a mis-splicing event in myotonic dystrophy type 1 that is induced neither by a loss of muscleblind-like 1 (MBNL1) function nor by a gain of CUGBP1 and ETR3-like factor 1 (CELF1) function but is rather associated to CUGBP1 and ETR3-like factor 2 (CELF2) gain-of-function.

Slowly progressive spinocerebellar ataxia with extrapyramidal signs and mild cognitive impairment (SCA21).

Spinocerebellar ataxia 21 is a slowly progressive and mild ataxia associated with extrapyramidal signs. Affected subjects exhibit a moderate gait and limb ataxia variably associated with akinesia, tremor, rigidity, hyporeflexia, and mild cognitive impairment. The responsible gene has been assigned to a 19 Mbases interval on chromosome 7p in a single French family. No evidence of significant linkage to this locus was found in 21 other families obtained from the EUROSCA consortium. The locus interval contains several candidate genes that could be responsible for the disease. Direct sequencing of NDUFA4, PHF14, KIAA0960, ARLA4, ETV1, DGKB, HDAC9, FERD3L, ITGB8, and SP4 genes were performed, but all the direct mutation analyses were negative excluding pathogenic mutations associated with the disease. Therefore, the gene responsible for SCA21 remains to be identified.

Is the early-onset torsion dystonia (EOTD) linked to TOR1A gene as frequent as expected in France?

Early onset torsion dystonia are rare movement disorders. Molecular defect is known for only a subgroup, consisting of a unique and recurrent mutation in the TOR1A gene. We undertook a nationwide census of French TOR1A-mutation carriers and the assessment of clinical associated signs. Overall, 53 index cases and 104 relatives were studied and haplotypes linked to the mutation constructed. The previously reported Ashkenazi-Jewish haplotype was found in 11 families with the remainder carrying distinct haplotypes suggesting independent mutation events. This study demonstrates the scarcity of this disease in France with estimated disease frequency of 0.13:100,000 and mutation frequency of 0.17:100,000.

Overexpression of MBNL1 fetal isoforms and modified splicing of Tau in the DM1 brain: two individual consequences of CUG trinucleotide repeats.

Neurofibrillary degeneration is often observed in the brain of patients with type 1 myotonic dystrophy (DM1). It consists principally of the aggregation of Tau isoforms that lack exon 2/3 encoded sequences, and is the consequence of the modified splicing of Tau pre-mRNA. In experimental models of DM1, the splicing of several transcripts is modified due to the loss of Muscleblind-like 1 (MBNL1) function. In the present study, we demonstrate that the MBNL1 protein is also present in the human brain, and consists of several isoforms, as shown by RT-PCR and sequencing. In comparison with controls, we show that the adult DM1 brain exhibits modifications in the splicing of MBNL1, with the preferential expression of long MBNL1 isoforms--a splicing pattern similar to that seen in the fetal human brain. In cultured HeLa cells, the presence of long CUG repeats, such as those found in the DM1 mutation, leads to similar changes in the splicing pattern of MBNL1, and the localization of MBNL1 in nuclear RNA foci. Long CUG repeats also reproduce the repression of Tau exon 2/3 inclusion, as in the human disease, suggesting that their effect on MBNL1 expression may lead to changes in Tau splicing. However, while an overall reduction in the expression of MBNL1 mimics the effect of the DM1 mutation, none of the MBNL1 isoforms tested so far modulates the endogenous splicing of Tau. The modified splicing of Tau thus results from a possibly CUG-mediated loss of function of MBNL1, but not from changes in the MBNL1 expression pattern.

GUG is an efficient initiation codon to translate the human mitochondrial ATP6 gene.

A maternally inherited and practically homoplasmic mitochondrial (mtDNA) mutation, 8527A>G, changing the initiation codon AUG into GUG, normally coding for a valine, was observed in the ATP6 gene encoding the ATPase subunit a. No alternate Met codon could replace the normal translational initiator. The patient harboring this mutation exhibited clinical symptoms suggesting a mitochondrial disease but his mother who carried the same mtDNA mutation was healthy. The mutation was absent from 100 controls and occurred once amongst 44 patients suspected of Leber Hereditary Optic Neuropathy (LHON) but devoid of typical LHON mutations. In patient fibroblasts, no effect of 8527A>G mutation could be demonstrated on the biosynthesis of mtDNA-encoded proteins, on size and the content of ATPase subunit a, on ATP hydrolysis and on mitochondrial membrane potential. In addition, ATP synthesis was barely decreased. Therefore, GUG is a functional initiation codon for the human ATP6 gene.

Real time RT-PCR shows correlation between retinoid-induced apoptosis and NGF-R mRNA levels.

Neurotrophins and retinoic acid have a critical role in the differentiation and the survival of neurons. All-trans-, 9-cis-retinoic acid (10(-6) M) or NGF (50-100 ng/ml) induced morphologic differentiation and inhibited cell growth in SH-SY5Y neuroblastoma cells after 7 days of culture. Continuous treatment of undifferentiated cells with all-trans- or 9-cis-retinoic (10(-6) M) did not induce apoptosis, whereas NGF-differentiated cells showed dramatic apoptosis after 2 to 4 days of retinoic acid treatment as evidenced by TUNEL reaction and flow cytometry analysis following propidium iodide staining. Addition of Ro41-5253 blocked all-trans-retinoic-induced apoptosis, suggesting that the apoptotic signaling pathway was mediated by RARs. The effects of all-trans- or 9-cis-retinoic acid on the expression of NGF receptors was evaluated using real-time fluorescence reverse transcription-PCR. A slight transient increase in the expression of p75(NGFR) mRNA was observed by 2 to 4 h after retinoid treatment of undifferentiated cells, whereas a larger increase in the expression of both TrkA and p75(NGFR) mRNA up to threefold the basal level, was observed by 2 to 6 h after retinoid treatment of NGF-differentiated cells. Our results suggest that NGF-differentiated cells may be more susceptible to retinoid-induced apoptosis than undifferentiated cells.

Dysregulation of human brain microtubule-associated tau mRNA maturation in myotonic dystrophy type 1.

Intraneuronal aggregates of hyperphosphorylated tau proteins, referred to as pathological tau, are found in brain areas of demented patients affected by numerous different neurodegenerative disorders. We previously described a particular biochemical profile of pathological tau proteins in myotonic dystrophy type 1 (DM1). This multisystemic disorder is characterized by an unstable CTG repeat expansion in the 3'-untranslated region of the DM protein kinase gene. In the human central nervous system, tau proteins consist of six isoforms that differ by the presence or absence of the alternatively spliced exons 2, 3 and 10. Here we show that the pattern of tau isoforms aggregated in DM1 brain lesions is characteristic. It consists mainly of the aggregation of the shortest human tau isoform. A disruption in normal tau isoform expression consisting of a reduced expression of tau isoforms containing the exon 2 was observed at both the mRNA and protein levels. Large expanded CTG repeats were detected and showed marked somatic heterogeneity between DM1 cases and in cortical brains regions analysed. Our data suggest a relationship between the CTG repeat expansion and the alteration of tau expression showing that DM1 is a peculiar tauopathy.

Clinical features and genetic analysis of a new form of spinocerebellar ataxia.

BACKGROUND: The autosomal dominant cerebellar ataxias (ADCA) are a clinically heterogeneous group of disorders. The mutations for SCA1, SCA2, SCA3, SCA6, SCA7, SCA8, and SCA-12 are identified and caused by an expansion of a CAG or a CTG repeat sequence of these genes. Six additional loci for SCA4, SCA5, SCA-10, SCA-11, SCA-13, and SCA-14 are mapped. The growing heterogeneity of the autosomal dominant forms of these diseases shows that the genetic etiologies of at least 20% of ADCA have yet to be elucidated. METHODS: The authors ascertained and clinically characterized a four-generation pedigree segregating an autosomal dominant phenotype for SCA. Direct mutation analysis, repeat expansion detection analysis, and linkage analysis for all known SCA loci were performed. RESULTS: Direct mutational analysis excluded SCA1, 2, 3, 6, 7, 8, and 12; genetic linkage analysis excluded SCA4, 5,10, 11, 13, and 14, giving significant negative lod scores. Examination of the family showed that all affected members had gait ataxia and akinesia with variable features of dysarthria, hyporeflexia, and mild intellectual impairment. Eye movements were normal. Head MRI showed atrophy of the cerebellum without involvement of the brainstem. In 10 parent-child pairs, median onset occurred 10.5 years earlier in offspring than in their parents, suggesting anticipation. CONCLUSION: This family is distinct from other families with SCA and is characterized by cerebellar ataxia and extrapyramidal signs.

Symptomatic hyperlactataemia: an emerging complication of antiretroviral therapy.

BACKGROUND: Fatal lactic acidosis is a serious complication of therapy with nucleoside analogues. OBJECTIVE: To examine symptomatic hyperlactataemia in HIV-infected adults treated with antiretroviral drugs. METHODS: In this prospective study, arterial blood lactate levels were measured in patients presenting with unexplained clinical symptoms. When these levels were high, functional respiratory tests (FRT) were carried out. Liver or muscle biopsies were further proposed. Incidences were calculated by comparison with the entire cohort of patients treated in the department. RESULTS: Fourteen HIV-infected adults treated with antiretroviral drugs were identified with symptomatic hyperlactataemia during a 2-year period follow-up study. The incidence of hyperlactataemia was 0.8% per year but reached 1.2% if only patients treated with a regimen including stavudine were considered. Clinical symptoms included abnormal fatigue, tachycardia, abdominal pain, weight loss, peripheral neuropathy, and more specifically exercise-induced dyspnoea occurring despite effective antiretroviral treatment. FRT showed a metabolic deviation towards anaerobiosis with a high lactate/pyruvate ratio. Ultrastructural mitochondrial abnormalities were seen in all four patients for whom this was examined. There was a marked decrease in complex IV activity in muscle biopsies from four of five patients, consistent with a mitochondrial dysfunction. Evolution was favourable in 13 patients, probably because of an early diagnosis. CONCLUSIONS: Potentially fatal adverse events occurring during antiretroviral treatment may be avoided by close monitoring of clinical signs and blood lactate levels. If other studies confirm that the cumulative long-term toxicity of antiretroviral drugs results from mitochondrial dysfunction, the incidence of hyperlactataemia and its clinical consequences may become more important.

The first identified French family with dentatorubral-pallidoluysian atrophy.

We report the first French family with dentatorubral-pallidoluysian atrophy (DRPLA) in which three members, a 36-year-old woman (proband), her 34-year-old sister, and 14-year-old brother were affected. There was no family history of DRPLA and their father presented at age 66 with pes cavus but without any other neurologic symptoms. Molecular analysis of the DRPLA gene from blood leukocytes showed CAG repeat sizes to be 68/16 in the proband, 62/15 in her father, and 16/16 in her mother. This study provides support for the variable clinical presentation of this disease with incomplete penetrance in the father and demonstrates that DRPLA can be observed in the French Caucasian population.

Cyclin-dependent kinase inhibitory protein expression in human choroidal melanoma tumors.

PURPOSE: Recent studies have demonstrated the close link between oncogenesis and cell cycle machinery. Cyclin-dependent kinase inhibitory proteins (CKIs) have been shown to play a critical role in the regulation of cell cycle progression. Alteration of CKI levels and/or functions could be implicated in cell transformation. The three CKIs-p16, p21, and p27-were investigated in human uveal melanoma tumors, and an attempt was made to correlate their levels with clinicopathologic parameters, as well as to p53 and Ki-67 (Mib-1) protein levels. METHODS: Immunochemistry was performed on 32 formalin-fixed, paraffin-embedded specimens of malignant choroidal melanoma. Immunoblot was performed to confirm the immunochemistry study. Prognostic histologic markers such as cell typing, pigmentation, larger tumor dimension, mitotic figures, nucleolar size, scleral invasion, and optic nerve head invasion were reported. RESULTS: Nuclear positivity for p16 was observed in 11 tumors (34%) without any association with clinicopathologic parameters. Tumor cells positive for p21 were detected in 12 choroidal melanomas (37%). Unexpectedly, a positive relationship was seen between p21 and scleral invasion (P: = 0.008). Nuclear positivity for p27 was observed in nine tumors (28%). An inverse correlation was observed between the number of mitotic figures and p27 immunoreactivity (P: = 0.03), as well as between Mib-1 positivity and p27 expression (P: = 0.02). Western blot assays of tumor extracts confirmed overexpression of p21 and p27. CONCLUSIONS: The results suggest that p21 and p27 may be involved in tumorigenesis in choroidal melanoma.

Absence of unidentified CAG repeat expansion in patients with Huntington's disease-like phenotype.

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by an expanded (CAG)n repeat on the huntingtin gene. It is characterised by motor, psychiatric and cognitive disturbances. Diagnosis can be confirmed by direct genetic testing, which is highly sensitive and specific and is now considered definitive. This study focused on 21 patients presenting with a clinical phenotype showing strong similarity to HD, but who do not have an expanded CAG in the huntingtin gene. However, other possible diagnoses could be evoked for most of them. Seven patients (3.5% of our cohort) could be considered as phenocopies of HD with no alternative diagnosis. Samples were screened for other triplet repeat diseases with similar presentation (DRPLA, SCA-1, SCA-2, SCA-3, SCA-6, and SCA-7) and were all negative. The repeat expansion detection technique (RED) was used to detect uncloned CAG repeat expansions and samples were also analysed by polymerase chain reaction for expansions of the polymorphic CAG-ERDA-1 and CTG18.1 trinucleotide repeats. RED expansion (>40 repeats) was detected in only one patient. The results suggest that unstable CAG/CTG repeat expansions corresponding to known or unknown sequences are not involved in the aetiology of HD-like disorders. It is hypothesised that some of these phenocopies could correspond to mutations in other unidentified genes with other unstable repeats (different from CAG) or in unknown genes with other mutations.

Critical role of tyrosine 277 in the ligand-binding and transactivating properties of retinoic acid receptor alpha.

Retinoic acid receptors specifically bind all-trans-retinoic acid (RA) and function as RA-inducible transcriptional regulatory factors. Binding of RA to RARalpha, beta, and gamma is sensitive to nitration with tetranitromethane, a tyrosine-specific modifying reagent. To identify tyrosine residue(s) that are important for RA binding, we carried out chemical modification experiments with purified RARalpha ligand-binding domain (RARalpha-LBD) subjected to partial acid hydrolysis and selective proteolysis. The chemically modified peptides containing each of the three Tyr residues present in the RARalpha-LBD sequence were then analyzed and identified by high-performance liquid chromatography coupled to electrospray ionization mass spectrometry (HPLC/ESI-MS). We found that RA binding to RARalpha-LBD protected Tyr(277)-containing peptides from nitration. Protection of Tyr(277) could result either from direct masking by the bound ligand or from ligand-induced changes in receptor conformation and tyrosine accessibility. The role of Tyr residues was further documented by site directed mutagenesis using three site-specific RARalpha mutants: Y208A, Y277A, and Y362A. The affinity for RA of these mutant receptors was in the range of that of the wild-type protein, except for the Y277A receptor mutant, which displays a 15-20-fold reduction in affinity and transactivation activity for RA. Whereas mutation of Tyr(277) into alanine had a variable effect on different agonists and antagonists binding, it caused a dramatic decrease of retinoid-dependent transactivation activity. This later effect was also observed with mutation of Tyr(277) into phenylalanine. It is unlikely that major conformational changes are responsible for the lower affinity of RA binding and RA-dependent transactivation since these mutants displayed wild-type dimerization and DNA-binding activities. Limited proteolysis revealed that upon ligand binding, the Y277A mutant induced a conformational change slightly different from that obtained with the wild-type protein. These data could suggest that Tyr(277) play a critical role in the ligand-induced conformational changes required for the activation of RARalpha.